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Nickel
Nickel is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements that exist around room temperature, the other three being iron, cobalt and gadolinium. The use of nickel has been traced as far back as 3500 BC, but it was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. Its most important ore minerals are laterites, including limonite and garnierite, and pentlandite. The metal is corrosion-resistant, finding many uses in alloys. Enzymes of certain life forms contain nickel as an active center, which makes the metal an essential nutrient for those life forms. Characteristics The electronic configuration of isolated nickel atom is counterintuitive: direct investigation finds that the predominant electron structure of nickel is Ar 4s1 3d9, which is the more stable form because of relativistic effects. Whereas Hund's rule, which works well for most other elements, predicts an electron shell structure of Ar 3d8 4s2 (the symbol Ar refers to the argon like core structure). This latter configuration is found in many chemistry textbooks and is also written as Ar 4s2 3d8, to emphasize that the 3d shell is the electron shell being filled by the highest-energy electrons. It is one of only four elements that are magnetic at or near room temperature. Its Curie temperature is 355 °C. That is, nickel is non-magnetic above this temperature. The unit cell of nickel is a face-centered cube with the lattice parameter of 0.352 nm giving an atomic radius of 0.124 nm. Nickel belongs to the transition metals and is hard and ductile. Naturally occurring nickel is composed of 5 stable isotopes; 58-Ni, 60-Ni, 61-Ni, 62-Ni and 64-Ni with 58-Ni being the most abundant (68.077% natural abundance). 62-Ni is the most stable known nuclide of all the existing elements, even exceeding the stability of 56-Fe. 18 radioisotopes have been characterised with the most stable being 59-Ni with a half-life of 76,000 years, 63-Ni with a half-life of 100.1 years, and 56-Ni with a half-life of 6.077 days. All of the remaining radioactive isotopes have half-lives that are less than 60 hours and the majority of these have half-lives that are less than 30 seconds. This element also has 1 meta state. 59-Ni has found many applications in isotope geology. 59-Ni has been used to date the terrestrial age of meteorites and to determine abundances of extraterrestrial dust in ice and sediment. Nickel-60 is the daughter product of the extinct radionuclide 60-Fe, which decays with a half-life of 2.6 million years. Because 60-Fe has such a long half-life, its persistence in materials in the solar system at high enough concentrations may have generated observable variations in the isotopic composition of 60-Ni. Therefore, the abundance of 60-Ni present in extraterrestrial material may provide insight into the origin of the solar system and its early history. Nickel-62 has the highest binding energy per nucleon of any isotope for any element (8.7946 Mev/nucleon). Isotopes heavier than 62-Ni cannot be formed by nuclear fusion without losing energy. Nickel-48, discovered in 1999, is the most proton-rich heavy element isotope known. With 28 protons and 20 neutrons 48-Ni is "double magic" (like 208-Pb) and therefore unusually stable. The most common oxidation state of nickel is +2, but compounds of Ni0, Ni+, and Ni3+ are well known, and Ni4+ has been demonstrated. Value The base value of each unit of ranges between 1 and 15Ð per unit, with up to 3 units being found at any one time. Presence on Mars: Common Category:Chemical elements